WO2018206789A1

WO2018206789A1 - Building material containing a binder and a fiber reinforcement

Info

Publication number: WO2018206789A1
Application number: PCT/EP2018/062250
Authority: WO
Inventors: Ralf Schäfer; Franz Weissgerber
Original assignee: Schäfer Elektrotechnik U. Sondermaschinen Gmbh; Carbon-Werke Weissgerber Gmbh & Co. Kg
Priority date: 2017-05-11
Filing date: 2018-05-11
Publication date: 2018-11-15
Also published as: DE102017110282A1

Abstract

The invention relates to a building material containing a binder and a fiber reinforcement of fibers, wherein the fibers are produced from recycled fiber material from comminuted molded parts, the fibers having a matrix.

Description

[Designation of the invention prepared by ISA according to Rule 37.2] BUILDING MATERIAL CONTAINING A BINDER AND A FIBER REINFORCEMENT

From the prior art it is known to provide a building material, such as concrete with a supplement in the form of a fiber reinforcement. The embedded in the building material fiber reinforcement improves the material properties of the building material and can, for example, prevent cracking in concrete components.

At present, fibrous materials such as glass fibers are used for fiber reinforcement, resulting in a composite of glass fibers and binder, such as cement. Here, the binder forms a matrix in which the glass fibers are embedded.

However, fiber material is also produced in large quantities in molded parts made of fiber composites. Fiber composites contain a fiber material as an essential component. This is often in the form of laminates, for example in the form of woven, laid or mats. The fibrous material is embedded in a matrix, which often consists of polymeric material, for example a thermoset such as synthetic resin. Fiber composite materials are processed in a wide variety of products and are used as molded parts or structural components, for example in shipbuilding, in aerospace technology, but also in consumer goods. Furthermore, rotor blades for wind turbines often comprise structural components made of fiber composite materials.

Structural components made from fiber composites have a limited life. For example, due to material fatigue it is necessary to replace rotor blades of wind turbines after about 10 years. An exchange is already premature if rotor blades with other geometries are to be mounted. Due to the large quantities of fiber composites, there is a need to recycle the material.

Here, however, is problematic that when using a matrix of thermosetting material such as synthetic resin no reversible melting of the matrix is possible.

In this respect, elements made of fiber composite material have hitherto, for example, been comminuted in such a way that the fiber composite material is in the form of a powder. Such a method is known, for example, from EP 0 473 990 A2. The process result, a powder, is then used as an additive for the production of new moldings. It is disadvantageous that the aggregate serves primarily as a filler and does not lead to an improvement in the material properties.

The invention has for its object to develop a process for the recycling of fiber composites whose process result crushing products that can be fed to a high-quality re-use.

This object is achieved with the features of claim 1. In advantageous embodiments, the dependent claims relate.

The building material according to the invention contains a binder and a fiber reinforcement, wherein the fiber reinforcement comprises fiber needles, wherein the fiber needles are produced from recycled fiber material from comminuted molded parts, wherein the fiber needles have fiber material and matrix.

In this respect, the fiber reinforcement of the building material according to the invention consists of recycled fiber material. The recycling takes place in such a way that matrix adheres to the fibers. Both the fibers and the matrix of the starting material are used to produce the fiber reinforcement of the building material.

In the process for the recycling of fiber composites elements containing fiber composite material are placed in a baffle reactor and comminuted by mechanical stress, the comminution takes place in such a way that arise as a shredded product fiber needles with adherent matrix.

It has hitherto been known from the state of the art to either reduce the size of elements, ie products or components comprising fiber composite material, such that the size reduction product is a powder. Alternatively, an attempt was made to completely separate the matrix from the fibers. However, it is problematic that the coating with which the fibers are pretreated to allow adhesion of the matrix, thereby removed and must be reapplied. In addition, the process is very complicated, since fiber material and matrix form a very strong bond. Furthermore, it is problematic that the fibers thus separated no longer reach the original strength of the original fiber material.

In contrast to the methods known from the prior art, it is desired according to the invention that the comminuted fiber material, the fiber needles, adhere to the matrix. The result of the process, that is to say the comminution products, are accordingly needle-shaped fiber elements consisting of fibers or fiber bundles which are encased in matrix. In this respect, both the fiber material and the matrix of the starting material is recycled.

In this case, the process management preferably takes place in such a way that break edges with an irregular shape result at the fiber needles, which improve the attachment of the binder of the building material. Accordingly, during comminution, the fiber composite is broken up and fiber fractions are separated together with the matrix.

The comminution product preferably contains fiber needles with a fiber length of 0.1 mm to 20 mm. A fraction may also contain fiber needles of greater or lesser fiber length. Preferably, the fiber length of 90 wt.% Of a fraction of crushed products from 0.1 mm to 20 mm. The comminution product particularly preferably contains fiber needles with a fiber length of 1 mm to 10 mm. From a fraction of elements which are comminuted in the impact reactor, therefore, fiber needles with adhering matrix in different fiber lengths, wherein the fiber length of 1 mm to 10 mm. The crushed product is free-flowing and can be processed in a mixer. In this respect, the shredded product, the fiber needles, can be further processed by simple means.

The starting material, the elements to be comminuted, contain about 30% by weight to% by weight matrix and 60% by weight to 70% by weight fibers.

The fiber needles of the aforementioned length form as a supplement for the building material fiber reinforcement. By arbitrarily aligning the fiber needles and a uniform distribution of fiber needles of different lengths arise on the one hand, an isometric strength behavior and on the other hand, a surprisingly high strength produced from the building material components. In this respect, the reprocessed fiber material in the form of the fiber needles can be fed to a high quality reuse.

A sieving line can be determined by sieve analysis for a large number of crushed products. In this case, it is conceivable, for example, to carry out a sieve analysis in each case for a fraction to be comminuted and to determine the grading curve for the comminuted fraction.

The sieving line shows the distribution of the fiber lengths of the shredded fiber needles of the crushed fraction. As a result, it can be determined which fiber length distribution the comminution products of the comminuted fraction have.

By mixing different fractions, which have different grading curves, it is thus possible to produce a predetermined fiber length distribution for a large number of comminuted products. This allows the production of molded parts with consistent product properties. In addition, it is conceivable to specify different formulations for different applications which should have a specific fiber length distribution. A concrete recipe can be achieved by targeted mixing of fractions of crushed products. Such a formulation has a uniform fiber length distribution.

An advantageous impact reactor has a cylindrical shell, which is provided on one end face with a bottom and on the other end side with a lid. The soil is assigned a rotatably mounted impact body. The cylindrical shell, the bottom and the lid include an impingement reactor space. The lid is provided with an opening for receiving the elements. The impact body may comprise chains or be formed as a rotor, which is provided with baffles.

In the peripheral region of the baffle reactor ejection openings can be arranged. The ejection openings are preferably associated with the jacket. The ejection openings can be closed by means of flaps. The ejection openings allow the discharge of the crushed products.

Preferably, the ejection openings are designed so that the crushed product can be continuously removed from the impingement reactor. It is advantageous that the residence time of the fiber composite material in the baffle reactor space is only very short, so that the mechanical action is limited by the impact body. A rejection of the crushing products already takes place when the desired fiber length is reached. It is advantageous here that a large part of the matrix still adheres to the fibers and that the fibers needles forming the shredded product have sharp and irregular break edges, which improves the attachment of new matrix.

The ejection openings can be covered with slotted or perforated cover plates. The slotted or perforated cover plates allow on the one hand a continuous discharge of the crushed products and on the other hand a discharge of the crushed products as soon as they have reached the desired fiber length. On the one hand thereby the residence time of the fiber composite material in the impact reactor is very short and on the other hand fiber needles with a large fiber length can be removed from the impact reactor.

In this respect, a continuous discharge of comminuted material takes place during the comminution of the elements. The crushed products leave the impact reactor immediately when they are crushed so far that they pass through the cover plates.

The choice of cover plates can be modified depending on a previously performed sieve analysis. The cover plates can be selected, for example, in terms of diameter and geometry of the through holes so that fiber needles can be discharged with a desired fiber length distribution from the baffle reactor.

There may be provided cover plates with differently sized through holes. As a result, a separation of fiber needles as a function of the fiber length can already take place during the discharge of the fiber needles from the impact reactor.

If it is desirable to carry out a further comminution, the cover plates can be closed by cover flaps.

In addition to the cover plates ejection flaps can be provided for ejecting large parts. This is particularly advantageous when composites with material combinations are processed in the impingement reactor. If the composite contains both metal components and fiber composite material, the fiber composite material in the form of the fiber needles is continuously discharged from the impact reactor during comminution. The metal content can then be removed via the discharge flap.

The baffle reactor may be associated with a classifier. This can be connected directly to the discharge opening. The classifier may comprise screens which allow sorting of the shredded products by fiber length. In this respect, a sieve analysis can be carried out after the discharge of the comminution products from the discharge opening, or the fibers can be sorted according to fiber length. This allows an advantageous combination of fibers with a certain fiber length. The advantageous selected fiber length distribution can also be achieved by the selection of cover plates described above. From this, especially high-quality new molded parts can be produced.

The fibrous material may contain glass fibers, carbon fibers, basalt fibers and / or aramid fibers. Although fiber composites made from glass fibers or basalt fibers are inexpensive, they also accumulate in a particularly large number of pieces. Composite fiber composites made from carbon fibers are particularly cost intensive and difficult to process. Due to the high strength, the reprocessing of such fiber composites has been difficult. However, it has been found that shaped articles produced from the fiber needles have very good material properties, in particular when the fiber needles comprise carbon fibers. The fiber needles forming the comminution product consist of bundles of carbon fibers to which matrix adheres.

In order for a solid matrix and fiber composite to form, fibers are sized. In this respect, for example, glass fibers are provided with glass fiber sizes and carbon fibers with carbon fiber sizes. The sizings deposit in the form of a coating on the fibers and improve the adhesion to the matrix. The fiber needles produced by the process of the present invention contain fibers having adhered size and adherent matrix. In this respect, it is not necessary to re-coat the fiber needles. The fiber needles can be embedded directly into a new matrix and processed into a molded part. The fact that the original sizing adheres to the fibers, a firm connection of the new matrix is guaranteed to the fibers. This results in moldings with surprisingly high strength values, although recycled fiber material is used.

The elements can be fed to a pre-crushing prior to crushing in the impingement reactor. By pre-crushing block-like elements can be produced from large moldings, for example from rotor blades of wind turbines, which can be filled into a baffle reactor. The pre-crushing can be done for example by sawing or water jet cutting. The resulting from the pre-crushing elements can then be transported by conventional conveyors such as conveyor belts and are free-flowing.

The building material may have a surcharge in addition to the fiber reinforcement. Preferably, the aggregate is in the form of an aggregate. The aggregate can be composed, for example, of gravel and sand in different particle sizes.

The building material may contain 85% by weight to 95% by weight of aggregate, 5% by weight to 15% by weight of binder and 0.001% by weight to 0.1% by weight of fibers. Surprisingly, it has been found that even a small amount of fiber reinforcement is sufficient to significantly improve the material properties of the building material.

The binder may contain cement. In this case, the building material may be formed as concrete, which is provided with a fiber reinforcement. Such a building material based on cement is particularly suitable for use in tunneling. In this case, the proportion of fiber reinforcement of recycled fiber needles may be up to 10% by weight.

According to an alternative embodiment, the building material may also contain the binder bitumen. In this case, the building material may be formed as asphalt. Such a building material based on bitumen is particularly suitable for use as a road surface in civil engineering. Here, investigations have shown that even a fiber reinforcement in a proportion of 0.001 wt.% Of the building material leads to a significant improvement in strength and load capacity.

In this respect, a road surface according to the invention contains a binder based on bitumen, an aggregate in the form of an aggregate and a fiber reinforcement in the form of recycled fiber needles.

The invention will be explained in more detail with reference to the figure. This shows schematically:

1 shows a baffle reactor for carrying out the method according to the invention.

FIG. 1 shows a baffle reactor 1 or a baffle reactor arrangement for comminuting elements which contain fiber composite material.

The starting material, for example, rotor blades of wind turbines, which have structural components in the form of embedded profiles of fiber composite material of carbon fibers. Such rotor blades can have a length of 60 m. In order for the material to be fed to the impact reactor 1, a preliminary comminution of the rotor blades takes place, in which block-like elements are formed. The pre-shredding is done by means of sawing.

Before the comminution, the starting product has about 35% by weight of matrix and 65% by weight of fiber material in the form of carbon fibers. The matrix is made of thermosetting synthetic resin and forms a strong bond with the carbon fibers.

The impact reactor 1 comprises a bottom 10 and a cylindrical shell 2 of metallic material. In the bottom area, inside the shell 2, a rotor 3 is arranged, which is provided with baffles 5. The rotor 3 is operatively connected to an electric motor 6, which is arranged outside the shell 2. The shaft connecting the rotor 3 to the electric motor 6 extends in the axial direction of the cylindrical jacket 2. The rotor 3 is provided with wings 4 which protrude radially from the shaft. At the ends of the free wings 4 baffles 5 are arranged. The baffles 5 are removably attached to the wings 4.

The impact reactor 1 is closed at the end face remote from the rotor with a cover 7, so that the bottom 10, casing 2 and cover 7 include a baffle reactor space. The lid 7 has a filling opening 9 for filling the elements. The jacket 2 is further provided at the height of the rotor 3 with an ejection opening 8 for discharging the crushed products. In the discharge opening 8 perforated cover plates 11 are used. The cover plates 11 form screens, which pass crushing products in the desired particle size.

For comminution, the pre-shredded elements are introduced via the filling opening 9 into the impingement reactor chamber. The elements are comminuted under the action of the rotor 3 provided with the baffles 5 to comminution products in the form of fiber needles and discharged through the discharge opening 8 from the baffle reactor space. The removal of the crushed product from the baffle reactor space takes place continuously in the present embodiment. The fiber needles are thus discharged immediately after reaching the desired fiber length.

Alternatively, the ejection opening can also be closed by a flap, so that the device is also suitable for batchwise operation.

The shredded products in the form of the fiber needles have a fiber length of 0.1 mm to 10 mm. The fiber needles consist of fiber material and matrix adhering to the fiber material. The fiber material in turn consists of fiber bundles and of sizing, which allows a firm adhesion of the matrix to the fiber material. In this respect, the fiber needles are still a composite material of fiber material and matrix. The fiber material is embedded in the matrix, with the fiber needles having sharp edges and irregular break edges due to comminution, which improves the adhesion of new matrix.

After comminution in the impact reeler 1, a sieve analysis is carried out using a fraction of fiber needles and a grading curve is determined. As a result, the fiber length distribution of the fraction is known and it can be prepared by mixing different fractions, a mixture of fiber needles with a predetermined fiber length distribution. The sieve analysis is carried out by sieves of the fiber needles in sieves with decreasing mesh size.

The building material contains a binder and a fiber reinforcement, wherein the fiber reinforcement comprises fiber needles, wherein the fiber needles are made of recycled fiber material from comminuted molded parts, wherein the fiber needles have fiber material and matrix. The fiber length of the fiber needles is from 0.1 mm to 10 mm. The building material also contains a supplement in the form of an aggregate.

The building material contains 85% by weight to 95% by weight of aggregate, 5% by weight to 15% by weight of binder and 0.001% by weight to 0.1% by weight of fiber needles.

According to a first embodiment, the binder contains cement. In this case, up to 10% by weight of fiber needles may be provided. An advantageous concrete building material comprises 80% by weight aggregate in the form of aggregate and sand, 15% by weight of binder in the form of cement and 5% by weight of fiber reinforcement in the form of recycled fiber needles.

In a second embodiment, the binder contains bitumen. An advantageous asphalt building material for use as a road surface comprises 89.999% by weight aggregate aggregate, 10% by weight binder in the form of bitumen, and 0.001% by weight fiber reinforcement in the form of recycled fiber needles.

Claims

Building material containing a binder and a fiber reinforcement, characterized in that the fiber reinforcement comprises fiber needles, wherein the fiber needles are made of recycled fiber material from comminuted molded parts, wherein the fiber needles have fiber material and matrix.
Building material according to claim 1, characterized in that the fiber length of the fiber needles is 0.1 mm to 20 mm.
Building material according to claim 1 or 2, characterized in that the building material contains a supplement.
Building material according to one of claims 1 to 3, characterized in that the building material 85 wt.% To 95 wt.% Supplement, 5 wt.% To 15 wt.% Binder and 0.001 wt.% To 0.1 wt.% Fiber needles contains ,
Building material according to one of claims 1 to 4, characterized in that the binder contains cement.
Building material according to one of claims 1 to 4, characterized in that the binder contains bitumen.
Road document containing a building material according to claim 6.